Rigid building frame with inflatable member

ABSTRACT

The invention describes a method of constructing a building involving the assembly of a rigid skeletal framework of struts defining the contours of the desired building which is for example domed, or part-barrel shaped. A membrane or envelope of plastics material is inflated within the framework to lift the struts from a state of compression under their own weight into a state of tension. The membrane is then coated on at least one side with settable material such as concrete or other glass fibre reinforced material and the membrane deflated when the material has set. In an example of the invention, support zones at the junctions of the struts support the set material.

BACKGROUND OF THE INVENTION

The invention is concerned with improvements in or relating to buildingconstruction. In particular the invention relates to a method ofconstruction in which a rigid framework is formed, the interstices ofwhich are subsequently infilled to form structures, panels, walls, andthe like, which are included in the context of this specification in thegeneral term being "buildings".

It has become increasingly popular to construct buildings particularlyof large ground plan area such as are suitable, for example, for hallsand exhibition sites from a rigid skeletal structure of steel struts ortubular members interconnected by means of connecting clamps. Thestructure is then clad with steel sheeting or screeded for layingconcrete thereupon to form a shell. Such a construction is, of course,under compression from its own weight and is only as strong as itsconnecting clamps.

A considerable amount of design work has therefore been necessary toproduce clamps of a strength commensurate with the strength of the steelstruts or tubes. This design work has been complicated by therequirements for many of these buildings to form part - cylindrical,domed or barrel-shaped spans of various plan areas. These shapes meanthat the angles at which the struts meet are variable not only frombuilding to building but also at different locations in the samestructure. Where it is desirable to avoid the necessity for themanufacture of these clamps in made-to-measure batches, attempts havebeen made to produce adjustable clamps. In order to achieve the strengthrequired, these adjustable clamps are relatively expensive to produce.

Moreover, such clamps are normally exposed to atmosphere and thereforesubject to corrosion, unless steps are taken to protect them, which addsto cost.

It is an object of the present invention to minimize reliance upon thestrength of the interconnecting clamps in a building of the abovedescription, so reducing the above disadvantages relating to this typeof building construction, and providing a method of construction whichis strong and relatively inexpensive.

It is also an object of the invention to obviate the need for theprovision of separate panels for incorporation into the structure andconsequent requirement for additional attachment points to theframework. Sealing problems are also avoided.

SUMMARY OF THE INVENTION

The invention therefore provides a method of building constructioncomprising the steps of (a) erecting a rigid skeletal framework ofstruts or tubular members to define the contours of the desiredbuilding, and securing the struts or members together at appropriateintersections thereof, (b) providing within said framework anair-impervious membrane so as to provide an airtight envelope, (c)inflating said envelope within the framework, (d) coating at least onesurface of the inflated membrane with settable material and (e)returning the air pressure within the envelope to normal.

Advantageously, the degree of inflation of the envelope in step (c) isgreat enough to take the framework from an as-assembled state ofcomponent compression between the struts or members to a state in whichthere is tension between the components, and wherein the externalsurface of the membrane is coated in step (d) with settable material, sothat when the air pressure is returned to normal within the envelope,the struts or members return to a non-tensioned state and detach fromthe newly set material, said material being arranged to remain incontact with support zones situated at the intersections of the strutsor members.

It will be appreciated therefore that the set material, which forms ahardened shell, is supported upon these support zones and thereforelongitudinally through the struts or members which are subjected tocompressive strain. Thus the struts or member may support a greaterweight of shell that in cases where the shell is in direct contact withthe struts, exerting a lateral pressure thereupon which tends to bendthe struts or members, causing probable failure.

Advantageously, the support zone comprises support plates secured tojoining devices to which are securable end portions of the struts ormembers.

Conveniently, the settable material is a suitable glass-fibre resin orconcrete and the finished construction is in a prestressed condition.

If desired, the settable material is applied to one surface only of themembrane, that surface which confronts the framework. The settablematerial is arranged completely to cover the framework and the membrane,which membrane may if desired be removed when the material is set. Wherethis exposes the inner side of the clamps, localized application ofsettable material, if desired, be made to the clamps to embed themcompletely and so protect and strengthen them.

Alternatively, the struts and clamps or other joining means may bepre-clad with a sleeving of, for example, expanded polyurethane. Thisprevents actual contact between the concrete and the metal of theframework and minimizes any risk of damage through differences inco-efficients of expansion. The clamps may also conveniently be encasedin polyurethane foam in order to isolate them from the framework.

In an example of construction according to the invention a building isconstructed by erecting a framework of steel tubing clamped together atappropriate intersecting portions of the tubing by clamping meanscomprising tubular sockets welded or otherwise assembled together atappropriate angles. Polyethylene or polyvinyl chloride (p.v.c.) membraneis introduced within the area defined by the framework and the marginsof the membrane secured in an air-tight manner to the flooring of thebuilding. Compressed air is then introduced into the envelope defined bythe membrane and the flooring to a pressure sufficient to take theweight of the steel tubing to an extent where the construction is nolonger under compression but is actually under slight tension. Aglass-fibre-reinforced resin or cement is then sprayed on the outsidesurface of the membrane so as to coat it and also to cover the frameworkof steel tubing and connecting clamps. When this coating is at thedesired thickness, the resin is allowed to set, and then the airpressure released. If desired, the membrane may then be carefullyremoved for re-use. The inner surfaces of the construction may then besprayed with the resin, at least in the regions of the connecting clampsto cover them completely. It will be understood that the membrane"balloons" out between the lengths of steel tubing so that the finishedconstruction has a 3-dimensional appearance which may be consideredaesthetically pleasing in comparison with a flat or plain curvedsurface, and has greater structural strength.

In an alternative example of the invention, a wall construction may beformed by first erecting a framework of steel tubing defining thecontours of a wall of the desired thickness. Tubular envelopes ofpolyethylene are then introduced side by side into the thickness of thewall so as to contact immediately neighbouring tubes when inflated.Resin of a suitable type is then sprayed onto each outer surface of thewall when the tubes are inflated. When the resin has set, thepolyethylene-lined cavities in the wall may be filled with foamedinsulating material to produce a strong, heat-insulating, fire-resistingwall construction which has been erected in a short time at a reducedcost compared with conventional walls.

A convenient form of framework may comprise a number of struts which maybe screwed together by means of a joining device having a plurality ofarms each provided with a screw-threaded end portion, the number of armsdepending on the design of the framework and generally being betweenthree and six.

It will be apparent that the arms radiating from a central hub portionare not usually in the same plane, the angles of the arms with respectto the central hub portion being calculated with reference to the shapeand size of the building.

Particularly in the assembly of a domed structure, it may well be foundthat a strut is required to be inserted between two joining devices, thepositions of which are already fixed. It is necessary then to introduceinto the construction of the strut a facility for a temporary reductionin the length thereof. The struts may therefore be formed in twoportions, one slidably received within the other to a limited extent ina telescopic manner.

It will be found convenient to incorporate into the framework of abuilding construction according to the invention an adjustable couplingdevice as described and claimed in British Patent No. 2018932, and alsoto introduce into this type of coupling device the facility to reduceits overall length in order to assist assembly.

There will now be described two examples of a method of buildingconstruction according to the invention. It will be understood that thedescription, which is to be read with reference to the accompanyingdrawings, is given by way of example only and not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a first domed building constructed according to the methodof the invention, in three steps of construction;

FIGS. 2 and 3 are plan and side views respectively of a joining devicesuitable for use in the framework of the first building;

FIG. 4 is an exploded view of an adjustable coupling device;

FIG. 5 is a view partly in section of the assembled coupling device;

FIG. 6 is an end view of a sleeve member of the coupling device;

FIG. 7 is a section on line VII--VII of FIG. 6;

FIG. 8 shows a second domed building constructed according to the methodof the invention, in three stages of construction;

FIG. 9 is a plan view of a joining device incorporating a support zone;

FIG. 10 is a side view (partly in section) of the joining device of FIG.9; and

FIGS. 11 to 13 are diagrammatic views (not to scale) of three stages ofoperation of the method of the present invention.

DETAILED DESCRIPTION

The building shown in FIG. 1 is a geodesic dome, the advantage of whichis that in such a structure, the components are already in a partialstate of tension.

Portion A of FIG. 1 shows a framework of steel tubing 2 interconnectedby clamp devices 4 which provide four, five or six connection points asrequired. The clamp device, may be any convenient type but preferably,as in this example, are selected to be capable of accepting end portionsof the tubing at appropriate angles. lt will be appreciated that theangles between the tubing varies both with the plan area of building andthe size of the vault, and it is convenient to supply to a suitablyprogrammed computer device details of the size of the required buildingand its components so that the clamps may be manufactured with thecorrect angles built-in, as explained below with reference to FIG. 2, ormay be adjustable so that the arms thereof may be pre-adjusted to thecorrect angle prior to erection.

Portion B of the drawing shows the framework infilled with an inflatedmembrane 6, which serves also to increase the tension in the components.

Portion C shows a coating layer of concrete 8 applied to cover theframework and the membrane.

FIGS. 2 and 3 show a clamp or joining device 4, which, as shown, havefour arms 12, each provided with a screw-threaded end portion 14 towhich is securable a strut 16. Where the building is to be clad inconcrete and it is desired to minimize the damaging effect of unevenexpansion and shrinkage of the concrete and the metal struts, it will befound advantageous to encase the device 4 is sleeving 18 of expandedpolyurethane and also to provide sleeving 20 on the struts 16.

The arms 12 of the joining device 4 will not normally lie in the sameplane when they are intended for use in a domed building. As mentionedabove, the exact value of the angle x shown in FIG. 3 will requirecalculation to produce a dome of the correct radius and plan area.

FIG. 4 shows a coupling device which may be used as part of theframework of a domed building, for example, to anchor the struts thereofto other struts or to a substrate.

The coupling device comprises U-shaped link 22 which engages a carrierlink 24 to which similar couplings may be attached. Leg portions of thelink 22 are provided with recesses 26 arranged to confront each otherand to receive a cross member 28 in the form of the circular head of abolt 30 which head is provided with two flats 32, one to engage each ofthe recesses 26. Surrounding the leg portions of the link 22 and thecross member 30 is a sleeve member 34, which is provided with an endwall 35 having three apertures 36, 38, 40 arranged to receive the twoleg portions and a threaded portion of the bolt 30, respectively.Grooves 42 in the inner surface of the sleeve member provide means torestrain the link member from rotary movement. An end surface 44 of thesleeve is provided with contoured portions 46 which co-operate with thecarrier link 24 (See FIG. 6).

An adapter member 48 comprises a bolt having a threaded bore 50 formedin the head thereof into which the threaded portion of the bolt 30 isreceived. A lock nut 51 is received on the externally threaded stemportion 53 of the member 48 together with a washer 54. The stem portion53 is received in an internally threaded member 55, which is receivedwithin a tubular strut 58, or a tubular end portion provided on a solidstrut, fitted over the member 55. Lip portions 56 of the strut 58 areinturned so as to retain the member 55 within the strut 58. It will beobserved that the strut is slidable on the stem portion 53 so as toallow for temporary reduction in the overall length of the device.

In order to facilitate the locking of the device in an extendedcondition, the lock nut 51 may be turned until the inturned edgeportions 56 of the strut 58 are trapped between the washer 54 and themember 55 into which the stem portion 53 is fulled screwed. The presenceof a further washer 59 insures a completely sealed fit.

It will be appreciated that as the adapter member is rotated to increasethe penetration of the bolt into the bore 50, so that the sleeve memberis forced in a direction towards the left of FIG. 5 by contact of aleading surface 60 of the adapter means against the end wall 35 of thesleeve member. The contoured portions thus engage and firmly clamp thecarrier link 21, thus preventing relative movement between the carrier24 and the link 22.

FIG. 8 shows a second geodesic dome similar in many respects to that ofFIG. 1.

Portion A of FIG. 8 shows a framework of struts of steel tubing 2'interconnected by clamps or joining devices 4' providing four, five orsix connection points, an example of which is shown in detail in FIGS. 9and 10.

Portion B of FIG. 8 shows the framework infilled with an inflatedmembrane 6' which serves to put the struts 2' into a state of tension toan extent where the struts tend to bow slightly outwardly.

Portion C shows a coating layer of concrete 8' applied to cover theframework and the membrane.

FIGS. 9 and 10 show details of one of the joining devices 4'. The devicecomprises a cylindrical body portion 62 to which are secured by screwthread means, for example, four struts 2, arranged at suitable angles toform the domed shape of the building. A support plate 64 is providedwhich is attached to a threaded spigot 66 projecting from the bodyportion 62.

Two adjacent support plates 64 are shown in FIGS. 11-13 linked by astrut 2'. FIG. 11 shows the strut 2' bowed slightly upwardly andoutwardly under the influence of the inflation of the membrane 6'.

A layer of concrete 8' is then applied to coat the membrane 6' and theplates 64. During this stage the weight of the concrete is partly borneby the bowed strut 2', but when the concrete has set and the envelope isno longer inflated, see FIG. 13, the strut 2' will re-straighten andmove away from the membrane-covered concrete 8' by a distance x. Thiswill leave the weight of concrete supported upon the plates 64 and notdirectly upon the struts. Thus the plates 64 provide the support zonessituated at the intersections of the struts. In this manner, the weightof the concrete shell will cause the struts to be under lengthwisecompression. The framework is therefore rendered more rigid andtherefore effectively stronger than if the weight of the shell were tobe received in a lateral manner on side surfaces of the struts.

It will be understood that the struts described may be solid or hollow.In the case of hollow struts, these may take the form of pipes linkedthrough joining devices provided with interconnecting bores for thepassage of liquids. For example, in a construction capable of utilizingsolar heat, water may be circulated through such a framework of pipes toconnect solar heating panels to a heated water storage container, forexample a hot water cylinder or a swimming pool.

In a further example of the invention the membrane is laid over theframework and settable material sprayed onto the underside of themembrane. There will, however, be a considerable gap exposed between themembrane and each strut where the strut surface curves away from themembrane and to avoid the use of excessive material in filling such gapsthey are filled prior to spraying of the material with lengths ofpacking material such as urethane foam. The lengths have suitablecross-sections, typically wedge-shaped. Alternatively, the gaps can beclosed off by tape or the like to leave air pockets on each side of thestruts.

1. A method of building construction comprising the steps of (a)erecting a rigid skeletal framework of struts or tubular members todefine the contours of the desired building, and securing the struts ormembers together at appropriate intersections thereof to form supportzones, (b) providing within said framework an air-impervious membrane soas to provide an airtight envelope, (c) inflating said envelope withinsaid framework at sufficient pressure to take said framework from anas-assembled state of component compression between the struts ormembers to a state in which there is tension between the components, (d)coating the external surface of said inflated membrane with settablematerial, and (e) returning the air pressure within the envelope tonormal thereby permitting the struts or members to return to anon-tensioned state and detach from the newly set material, saidmaterial being arranged to remain in contact with support zones situatedat the intersection of the struts or members.
 2. A method as claimed inclaim 1, wherein each support zone comprises a support plate secured tojoining devices to which are securable end portion of the struts ormembers.
 3. A method as claimed in claim 2, wherein the settablematerial is applied only to that surface of the membrane which confrontsthe framework.
 4. A method as claimed in claim 3 wherein the membrane isremoved when the settable material has set.
 5. A method as claimed inclaim 4 wherein the joining devices exposed by the removal of themembrane are then coated by localized application of amounts of settablematerial thereto.
 6. A method as claimed in claim 4 wherein the strutsor members and the joining devices are pre-clad with a sleeving ofisolating material.
 7. A method as claimed in claim 1 wherein theframework is arranged in two shell formations one within the other todefine the contours of a wall of a desired thickness, the membrane beingformed into a plurality of tubular envelopes introduced into thethickness of the wall between the shells and inflated so as to contactneighbouring envelopes.
 8. A method as claimed in claim 7 wherein theinflated envelopes are filled with foamed insulating material.
 9. Amethod as claimed in claim 1 or 7 wherein the struts or members arehollow pipes linked through joining devices provided withinterconnecting bores for the passage of liquids.
 10. A method asclaimed in claim 1 or 7 wherein at least a proportion of the struts andmembers employed are adjustable lengthwise in a telescopic manner tofacilitate assembly.